Disease Analysis And Reinforcement Design Of Inclined Cracks In WEB Of Prestressed Continuous Box Girder Bridgr

Prestressed continuous girder bridges have many advantages,such as small structural deformation,large stiffness,strong spanning ability,good integrity and so on.They are loved by more and more people,and then they are popularized and applied vigorously.The number of prestressed continuous girder bridges is constantly increasing.However,due to the increase of highway traffic volume,the improvement of vehicle carrying capacity,the aging of building materials and other reasons,all kinds of diseases of this kind of bridge have appeared one after another,which will affect the durability of the bridge,and seriously affect the safety of highway transportation.In this paper,through a practical project of a prestressed reinforced concrete box girder bridge,the main diseases of its Web diagonal cracks are analyzed and studied in theory,and then the reinforcement scheme is determined and the bridge after reinforcement is evaluated.(1)The theoretical knowledge of cracks in prestressed concrete continuous box girder bridges is studied and summarized.The finite element analysis software MIDAS CIVIL is used to model a common pre-stressed concrete bridge.The influence of prestress loss,temperature load and other factors on the principal tensile stress of the web of the main girder is analyzed and compared.The stress loss of prestressing tendons is the main factor affecting the principal tensile stress of the main joints of web beams.(2)According to the theoretical calculation of the upper part of the K36+661 separation bridge in the west section of Harbin Circle Highway(Wapanyao-Qinjia),which is a practical project,the principal tensile stress and principal compressive stress of the section meet the requirements of the code,and the stirrups in the original design meet the requirements of shear resistance.In the ultimate state of bearing capacity,the bending strength of normal section and shear strength of oblique section meet the design requirements.(3)The main disease of K36+661 separation bridge was found to be serious Oblique cracking of Web by appearance inspection.Through load test,the web near the four-point of the middle span of the bridge appeared serious cracking due to overload of vehicles,but the bearing capacity of the bridge can meet the requirements of automobile-overload 20,and the overall working condition of the bridge is good..After determining the main factors affecting the durability and safety of the bridge,it is decided to carry out maintenance,renovation and local bearing capacity reinforcement for the bridge.(4)Determine the reinforcement scheme,and simulate the whole bridge after reinforcement according to the reinforcement scheme.The results are compared before and after reinforcement.Finally,the expected reinforcement effect is described.